Snape gulped as he he saw the jet of green light erupt from his wand and hit Dumbledore's chest, blasting the old wizard into the air. For a split second he seemed to hang suspended beneath the shining skull, and then he fell slowly backwards, over the battlements and out of sight. Snape couldn't believe he had actually done what Albus had asked.

He had also kept his Unbreakable Vow, but he still had to get Draco out of Hogwarts as soon as possible.

'Out of here, quickly,' ordered Snape. Draco was still paralyzed with shock and unable to look after himself, so Snape seized the boy by the scruff of the neck and forced him through the door. Together they sprinted down the spiral staircase, into the dimly lit corridor where the fight still raged. Snape made sure they were at the next door before shouting, 'It's over, time to go!'

Then they were outside the castle, on the grounds. 'Run, Draco, and Disapparate as soon as you are outside the school's boundaries, do you understand me?' he said urgently. Draco's eyes were wide and his pale face looked even more unhealthy in the greenish light of the Dark Mark. But he seemed to have regained some measure of his composure, because he gave a quick nod and started running, with Snape following him as fast as he could. When the boy reached the boundaries and managed to Disapparate, Snape felt deeply relieved. He stopped running and, panting, walked the last meters to the spot where Draco had would stay here for a moment longer to make sure that all Death Eaters left the school before they could cause any more harm. He turned around and stared at the castle.

There was movement! Potter was racing out of the building, straight at him, Alecto just a few meters behind him. When she threw a curse at Potter, Snape only just managed to erect a shield in time. However, the energy that erupted when the curse hit the shield was such that it sent Potter flying to the ground, and the deflected curse set a nearby bush on fire.

'No!' Snape yelled at the witch. 'Have you forgotten our orders? Potter belongs to the Dark Lord! We are to leave him! Go! Go!! You, too, hurry up!' he yelled at the other Death Eaters that had meanwhile arrived.

Thankfully, she and the other Death Eaters listened to him and Disapparated. Snape breathed a sigh of relief. It would have been fatal if he had managed to save Draco but had lost Potter in the process to some overenthusiastic Death Eater.

Snape watched as Potter scrambled to his feet and quickly covered the rest of the distance that seperated him from Snape. Maybe there was still time to give him a few instructions. He had just saved the boy's life – again! - and at least until Flitwick woke up and was in condition to report that Snape had attacked him, Potter had no reason to suspect that he had been doing more than his usual spying duties for the Order.

After all, Potter had finally started to trust him a few weeks ago, and they had managed to get along without any major conflicts since that time. However, one glance at Potter's face, illuminated by the burning bush, showed nothing but deep hatred and rage.

'Sectumsempra!' yelled Potter, waving his wand wildly. Snape deflected the spell with a quick flick of his own wand. Where did Potter's sudden loathing come from? Had he been up on the Tower as well?

If so, he would have had to have been under his Invisibility Cloak. But then why hadn't he interfered? Snape hissed as he fit the pieces together: Potter must have been there, Immobilized by Albus. There was no other explanation.

Albus... The frustration and sadness he felt about what he had had to do nearly overwhelmed him once again, but the expression on the face of the boy before him brought him back to his duty.

'You dare use my own spell against me, Potter?' he hissed dangerously. 'It was I who invented it – I, the Half-Blood Prince!' And it was the first real Dark spell I invented, he thought, somehow it all started with this...

His revelation only infuriated Potter even more.'Stupefy!' Another red jet of light flew at him, which he blocked easily. Rage didn't make Potter a more dangerous opponent, quite the opposite.

'You will never win a duel if you don't master nonverbal spells, Potter!' he spat at the boy. What was happening to him? His teaching career was undoubtedly over, still... Potter needed to learn, he needed training! Where was he going to get it? It was almost certain that the Dark Lord would take Hogwarts over soon, and Potter would not be able to fnish his education there, nor would his friends. Oh Albus, you left us all far too soon...

What had Albus been thinking? One day in the future, Snape was supposed to tell the boy that he had to die in order to defeat the Dark Lord for good. Now that Potter had witnessed him killing Albus, how was he supposed to make Potter believe him about the fragment of the Dark Lord's soul inside him? Now Potter would surely believe it to be a lie, and a rather pathetic one at that.

'Crucio!' His shield was almost too late this time. If he didn't concentrate, the boy might win this duel in the end, and that mustn't happen. The price he had paid to gain his position as the Dark Lord's most trusted servant had been far too high.

Expelliarmus! His own nonverbal spell brought success instantly. Potter's wand flew high into the air, and with a swift momvement of his arm that would have made any Seeker envious, Snape caught it. 'No Unforgivables from you, Potter!' he commanded. This was definitely no classroom setting, but he couldn't afford to lose any opportunity to train the boy, as absurd as the timing might be. 'You have neither the ability nor the nerve!'

The boy, although disarmed, was far from giving up. Fists raised, he flung himself at Snape Muggle-style. A Jelly-Leg-Jinx dropped him to the ground, cursing. Snape approached him and the boy, unable to stand, sat up and looked into his face.

Snape could see hatred, but no trace of fear in the boy's countenance. ' Kill me, then,' Potter panted. 'Kill me like you killed him, you coward!'

Snape heard the blood thunder in his ears. Coward? When he had just destroyed the only real protector that he had and signed his own death warrant? 'Never... ' - his wand whipped through the air – '... call me a ... ' – another whipping movement of his wand followed, this time in the opposite direction – '... coward!' he hissed furiously. Potter cried out and his hands flew to his face where, on each cheek, an angry red welt had appeared.

Snape lowered his wand. The lashing hex, though not dangerous, was extremely painful. Why had he thrown it at Potter; what had he expected? Potter had seen him kill an unarmed man. His reaction was logical and just a taste of what everybody would be saying. Despair made breathing difficult for a moment.

Potter glanced at his fingers as if checking for blood, then looked accusingly at Snape again. 'Dumbledore trusted you absolutely,' he said, tonelessly.

'Yes, Potter.' Snape's voice was no more than a hoarse whisper. 'He did.'

'How could you!' Potter's voice broke and the indictment in his tone caused a chill to run down Snape's spine. Yes, Potter, I myself wonder how I could. To focus enough to be able to use Avada Kedavra on the one living person I care most about… Albus, I hope you are proud of me, Snape thought bitterly.

'And I trusted you, too.' The boy's soft words were hardly audible. Snape felt a lump in his throat. Not long ago he wouldn't have cared less about Potter's opinion of him, but now he found Potter's disappointment almost unbearable. He longed to shout out that he had been following Dumbledore's orders, but that was out of the question. Potter would never be able to keep that knowledge to himself.

'I did what had to be done,' Snape said quietly, internally wondering if he was already going too far with his cryptic hint, 'as you will have to do one day, Potter.'

Potter still was staring at him, his face a mixture of grief and confusion. 'Professor Dumbledore trusted you absolutely,' he repeated, though his tone was less accusing than before.

Snape wondered if it was possible that he had planted the seed of a doubt in Potter's mind. It would be more than he could have asked for, and maybe already more than it was safe to do. But the vague possibility was a definite, albeit very small, consolation.

Potter opened his mouth, and closed it again, without saying anything. Tears were running down his cheeks as he silently scrutinized Snape, searching for answers in his eyes. Staring into the boy's pale face Snape couldn't ignore the fact how much the boy had matured over the last few months. 'And I am sure, Mr Potter,' he added, 'that when the time comes, you, too, will be able to do what needs to be done.'

Never before had he expressed such confidence in Potter, but in that moment he knew the boy would not shrink back from his duty. Maybe, just maybe, there was still hope for all of them. Well, except for Potter. He was surprised by the intensity of grief he felt at the thought of the inevitability of the boy's death. As to how he was supposed to deliver the Headmaster's last message to Potter, he would have to solve that problem later.

Voices could be heard and he saw a group of people coming out of the castle. There was no time to lose.

Snape raised his wand. Potter had his gaze fixed on him but didn't flinch. 'Finite.' Snape undid the Jelly-Leg-Jinx and threw Potter's wand to the boy. Potter caught it, too bewildered to use it straight away.

Snape looked a last time into the boy's face, desperately hoping it was not the last time he would see the boy alive. There was nothing left to say, or rather, there were hundreds of things to say, but it was too late.

Snape suddenly realized that Albus had been right when he had suggested that Snape tell Potter about his involvement with his mother. Well, that was just another one of the numerous chances he had missed in his life. But this was definitely not the moment. So with a stiff nod to Potter, Snape turned on the spot and Disapparated.

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So FINALLY the story is complete. I know it's a rather sad ending and probably not what some of you expected, but given the context, with Voldemort about to take over and a war about to start, I found it rather hard to come up with something cheerful...

As always, reviews are more than welcome, I am really curious to read what you think!